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Chapter 4: Chapter 4: HeatHeat

Form 4Form 4

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PhysicsPhysicsNext >

The study of The study of mattermatter

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Objectives: Objectives: ((what you will learnwhat you will learn)) 1) understanding Heat as a form of

Energy

2) understanding the Laws

Physics: Chapter Physics: Chapter 44

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HeatHeat

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Heat is a form of energy.

It flows from a hot body to a cold body.

SI unit: Joule (J)

Amount of heat in a body depends on:• Mass of object• Temperature of object• Type of object

Temperature is the degree of hotness of a body.SI unit: Kelvin (K)

Any physical property of a body which varies uniformly with temperature will serve as a measure of temperature.

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HeatHeatWhen 2 bodies are in thermal equilibrium, there is no net flow of heat between the two bodies.

Specific heat capacity, c of a substance = amount of heat neede to raise temperature of 1 kg of the substance by 1oC. It is measured in J kg-1 C-1.

Amount of heat of a body, Q = mcӨwhere m = mass of object

c = specific heat capacityӨ = change in temperature

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Specific latent heat of fusion is the heat needed to change 1 kg of a substance from solid state to liquid state without any change in temperature.

It is also the amount of heat needed to change 1 kg of the substance from liquid state to vapour state without any change in temperature.

HeatHeatLatent heat absorbed or released during the change in states,

Q = ml

where m = mass of object l = specific latent heat

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Boyle’s Law

The volume of a fixed mass of gas is inversely proportional to pressure provided temperature is constant.

Charles’ Law

The volume of a fixed mass of gas is directly proportional to its absolute temperature provided the pressure remains constant.

The LawsThe Laws

P1V1 =

P2V2

V1 V2

T1 T2

=

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Pressure Law

The pressure of a fixed mass of gas is directly proportional to its absolute temperature provided the volume remains constant.

General Gas Law

Summarizes Boyle’s Law, Charles’ Law and Pressure Law.

The LawsThe Laws

P1 P2

T1 T2

=

P1V1 P2V2

T1 T2

=

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Relationship between Celcius and Kelvin.

ӨoC = (Ө + 273) K

The temperature of –273oC is the minimum temperature which can be achieved by the gas.

This temperature is known as absolute zero.

The LawsThe Laws

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SummarySummary

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What you have learned:What you have learned:

1.1. Understanding Understanding Heat Heat as a form ofas a form of EnergyEnergy

2.2. Using theUsing the Laws Laws

Thank YouThank You